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It’s still early days for efforts to develop gene therapies against hemophilia, but a handful of patients treated with these one-time, potentially curative treatments have now been followed long enough to start measuring clinically relevant outcomes like reductions in bleeding episodes. That’s what matters most to hemophilia patients (and it’s what will form the basis of regulatory approvals), so it’s more significant than looking at surrogate markers of activity such as increases in the activity level of clotting factors.

On Tuesday, Biomarin announced plans to start a phase 3 study in the fourth quarter of its gene therapy BMN 270 for hemophilia A. The biotech company is moving forward with the high dose of BMN 270, which some will see as a controversial decision because Factor VIII activity levels exceeded normal limits in some patients treated in the phase 1-2 study.


A quick look at those BMN 270 data from the phase 1-2 study, also announced Tuesday: At the high dose level, the mean annual bleed rate fell from 16.3 to 0.5. At the median, the annual bleed rate dropped from 16.5 to zero. Those are strong results. This was in six patients with severe hemophilia A who required prophylactic injections of Factor VIII before treatment with BMN 270. All patients were followed for at least one year after receiving BMN 270.

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